Shanghai (M, 1 entry) -> Hong-Kong (3days, no visa) -> Shanghai (72 hours transit permit-> Germany

Hello,

I'm working in Shanghai for 3 month. I've got a M with one entry. Before I return to Germany, I would like to visit Hong-Kong for a few days. I would like to let my big luggage at my hotel in Shanghai and only travel with a little backpack. Is it possible to leave Shanghai for 3 days for travelling to HK, then return to Shanghai, get a 72 hours permit, go to my hotel, sleep for a night there and then return to Germany?